External link from the template

I know it should be simple, but since I am into silverstripe some months ago I have sometimes problem with smallest things.

I am trying to generate in my template one picture with a link to external site. This link will be written by my customer when he makes and entry in the cms, so will come from DB. The problem is, the link is coming right, but the finall result is link with the baseurl in the href that look like this "http://mydomain/parentpage/http://www.google.es".

sorry I had left this project for a moment to focus on anothers. I forgot totally about my post.

I am trying your solution, but it doesn´t work, the issue I think is different, how SS handle the template and treats the <a href> tags. Because the $ExternalLink is showing right if I place it in h2 for example.

I mean if I even use static word for example:

<a href="Hellloworld" rel="external">linkName</a>

SS is adding the baseUrl before Helloworld when build the template, so the final:

href --> 'http//www.baseurl.com/dataObject/Helloworld'

What I want to get is href --> 'Helloworld' only to then I build my link on my own.